Improved flow pattern map for accurate prediction of the heat transfer coefficients during condensation of R-134a in smooth horizontal tubes and within the low-mass flux range

Suliman, Ridhwaan; Liebenberg, Leon; Meyer, Josua P.

doi:10.1016/j.ijheatmasstransfer.2009.08.017

Cited by 37 publications

(26 citation statements)

References 21 publications

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“…The experimental system (Figure 1) was inherited from past research work in which detailed descriptions and explanations have been provided (Adelaja et al, 2014a(Adelaja et al, , 2014bCanière et al, 2007;Lips and Meyer, 2012a, 2012b, 2012cMeyer et al, 2014;Suliman et al, 2009;Van Rooyen et al, 2010). Therefore, only a brief overview will be provided in this section.…”

Section: Experimental Set-upmentioning

confidence: 99%

The influence of inclination angle on void fraction and heat transfer during condensation inside a smooth tube

Olivier

Meyer

Paepe

et al. 2016

International Journal of Multiphase Flow

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Most work in literature on condensation in tubes has been done for smooth tubes in the horizontal and vertical configurations. Recent experimental works with condensation at different inclination angles showed that the heat transfer characteristics were a function of inclination angle. These works were limited to heat transfer and pressure drop measurements with visual observations. However, no work has been done on measuring the void fractions during condensation at different inclination angles. The purpose of this study was to measure void fractions and heat transfer coefficients during condensation for tube inclinations ranging from vertical downwards (-90ᵒ) to vertical upwards (90ᵒ) at a saturation temperature of 40 ᵒC. Measurements were taken in an experimental set-up in which condensation occurred on the inside of a test section. The test section was a circular tube with an inner diameter of 8.38 mm and a heat transfer length of 1.488. The refrigerant used was R134a, and the void fractions were measured using two capacitive void fraction sensors. Mass fluxes ranging from 100 -400 kg/m 2 .s and vapour qualities ranging from 10 -90% were considered. Heat transfer coefficients were also compared with void fractions. It was found that at combinations of low mass fluxes and vapour qualities, void fraction and heat transfer were significantly affected by changes in inclination angle. Generally, void fractions and heat transfer coefficients increased with downward inclination angles with an optimum angle between -10ᵒ and -30ᵒ (downward flow). At some intermediate mass flux and vapour quality conditions, the void fraction and heat transfer coefficients were observed to be independent of the inclination angle despite changes in the prevailing flow patterns.2

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Section: Experimental Set-upmentioning

confidence: 99%

The influence of inclination angle on void fraction and heat transfer during condensation inside a smooth tube

Olivier

Meyer

Paepe

et al. 2016

International Journal of Multiphase Flow

View full text Add to dashboard Cite

show abstract

“…The experimental facility used in this study was adapted from the one already presented in previous work [16,17], and is therefore only briefly described. The set-up consisted of a vapourcompression cycle circulating the refrigerant R134a with a nominal cooling capacity of 10 kW and with two high-pressure condensation lines: the test line and the bypass line (Fig.…”

Section: Experimental Set-upmentioning

confidence: 99%

“…This deviation may be partially explained by the presence of oil in the refrigerant that tends to decrease the heat transfer coefficient in the condenser. According to previous studies [16,17] performed on the experimental set-up, the amount of oil can be estimated between 0.5 % and 3%. Another cause of the deviation can come from the temperature measurement uncertainties (especially on the water side because of the low water velocities) and the correlation uncertainties.…”

Section: Effect Of Inclination Angle On Heat Transfer Coefficientsmentioning

confidence: 99%

Experimental study of convective condensation in an inclined smooth tube. Part I: Inclination effect on flow pattern and heat transfer coefficient

Lips

Meyer

2012

International Journal of Heat and Mass Transfer

117

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An experimental study of convective condensation of R134a in an 8.38 mm inner diameter smooth tube in inclined orientations is presented. This article, being the first of a two-part paper (the second part concentrates on the pressure drops and void fractions), presents flow patterns and heat transfer coefficients during condensation for different mass fluxes and vapour qualities for the whole range of inclination angles (from vertical downwards to vertical upwards). The results were compared with three flow pattern maps available in literature. It was found that for low mass fluxes and/or low vapour qualities, the flow pattern is strongly dependent on the inclination angle whereas it remains annular for high mass fluxes and high vapour qualities, whatever the tube orientation. The models of flow pattern maps available in the literature did not predict the experimental data well. In the inclination-dependent zone, experiments showed that there is an optimum inclination angle that leads to the highest heat transfer coefficient for downward flow. The heat transfer coefficient is strongly affected by the liquid and vapour distributions and especially by the liquid thickness at the bottom of the tube for stratified flows. Thus developing a mechanistic model of flow pattern maps is the first step in achieving a predictive tool for the heat transfer coefficient in convective condensation in inclined tubes.

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“…This flow pattern map was built from that of Kattan et al (1998), which was an extension of that of Steiner (1993) and that of Taitel and Dukler (1976). The map and the heat transfer correlation were slightly improved by Suliman et al (2009) Müller-Steinhagen and Heck (1986) was the best for annular flows while the method of Grönnerud (1972) gave the best predictions for both intermittent and stratified-wavy flows. As a consequence, there is a need for a general mechanistic model.…”

Section: Condensation In Horizontal Smooth Tubesmentioning

confidence: 99%

Two-phase flow in inclined tubes with specific reference to condensation: A review

Lips

Meyer

2011

International Journal of Multiphase Flow

106

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Improved flow pattern map for accurate prediction of the heat transfer coefficients during condensation of R-134a in smooth horizontal tubes and within the low-mass flux range

Cited by 37 publications

References 21 publications

The influence of inclination angle on void fraction and heat transfer during condensation inside a smooth tube

The influence of inclination angle on void fraction and heat transfer during condensation inside a smooth tube

Experimental study of convective condensation in an inclined smooth tube. Part I: Inclination effect on flow pattern and heat transfer coefficient

Two-phase flow in inclined tubes with specific reference to condensation: A review

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